The wife and I are leaving feb 23 on Liberty. We intend on purchasing the unlimited coke/diet coke for the week. If only one of us got it, could that person get 2 diet cokes at a time, or should we bite the bullet and both purchase the coke/diet coke?

The rule is one drink package per person. They also won't give one person more than one drink at a time. On RCI they put a stamp on your cruise card when you buy a drink package. You have to show the card to get a glass of soda.

On my last cruise I took my friends soda container to have it filled for her, and was asked for my card. I told the bartender I was just haven't it filled for my friend--and was denied. It seems they're watching the soda thing a little closer than before. I've seen some people pour soda into another container and go back for the second fill. At least two people didn't have to go up to the bar. While having lunch in the windjammer, they usually don't ask for the card, they just take your container and fill it for you.

Sonny is right. On some earlier RCCL cruises, the bartenders were a little relaxed in their policies. I would take both containers and the bartender would fill both without my wife being present. On recent cruises, that has not been the case. They want both cards present to fill both containers. Even bartenders that I have tipped well on previous encounters have been pressured by their superiors to fully enforce the "one coke at a time per card" rule.

Happened with us too. The bartender in question apologized profusely for asking for my son's card each time and said his bar manager would give him endless grief otherwise. It didn't bother me and I told him he was doing his job and shouldn't apologize for it.

Sorry, but once again I have to state that I think that the soda-stamp deal onboard is a rip-off. Ture you get this cute SMALL soda cooler-tumbler type holder, but, once filled with ice, holds MAYBE half a can of soda.
On our last trip, I found that using my sea pass card account, I could buy a whole can of soda for about $1.50 each, and they would give you a glass if ice too if you asked.
On our first cruise, we both bought the stamp for about $85-$90 for both. We ended up maybe dringing three full cans of soda each for the entire 7 days-so unless you are a major soda drinker, I'd pass on the stamp. It just seemed like an unnecessary expense, and , in my opinion, a large money maker for the cruise line. Use the extra cash you save for something nice to remember your trip (photos are another big expense, but at least you have something nice to look at and remember)
Iced tea (for those who like it), is free.
Have a great cruise!!

Sorry, but once again I have to state that I think that the soda-stamp deal onboard is a rip-off.

Me too - more so for adults. We get the stamp for our son since it makes it easier for him to get his own drinks, but I cannot recommend the soda stamp for adults.

I just did a test on our son's souvenir cup from the Liberty last year. With no ice it holds 20 ounces of liquid. I put crushed ice in and it took up about half the volume and I could only get a little over 8 ounces of water in the cup.